Diarrhea is the reversal of the normal net absorptive status of water and electrolyte absorption to secretion. The augmented water content in the stools (above the normal value of approximately 10 mL/kg/d in the infant and young child, or 200 g/d in the teenager and adult) is due to an imbalance in the physiology of the small and large intestinal processes involved in the absorption of ions, organic substrates, and thus water.
Signs and symptoms
Acute diarrhea is defined as the abrupt onset of 3 or more loose stools per day and lasts no longer than 14 days; chronic or persistent diarrhea is defined as an episode that lasts longer than 14 days. The distinction has implications not only for classification and epidemiologic studies but also from a practical standpoint, because protracted diarrhea often has different etiologies, poses different management problems, and has a different prognosis.
The clinical presentation and course of diarrhea therefore depend on its cause and on the host. Consider the following to determine the source/cause of the patient’s diarrhea:
Stool characteristics (eg, consistency, color, volume, frequency)
Presence of associated enteric symptoms (eg, nausea/vomiting, fever, abdominal pain)
Use of child daycare (common pathogens: rotavirus, astrovirus, calicivirus; Campylobacter, Shigella, Giardia, and Cryptosporidium species [spp])
Food ingestion history (eg, raw/contaminated foods, food poisoning)
Water exposure (eg, swimming pools, marine environment)
Camping history (possible exposure to contaminated water sources)
Travel history (common pathogens affect specific regions; also consider rotavirus and Shigella, Salmonella, and Campylobacter spp regardless of specific travel history, as these organisms are prevalent worldwide)
Animal exposure (eg, young dogs/cats: Campylobacter spp; turtles: Salmonella spp)
Predisposing conditions (eg, hospitalization, antibiotic use, immunocompromised state)
Signs and symptoms of diarrhea may include the following:
Dehydration: Lethargy, depressed consciousness, sunken anterior fontanel, dry mucous membranes, sunken eyes, lack of tears, poor skin turgor, delayed capillary refill
Failure to thrive and malnutrition: Reduced muscle/fat mass or peripheral edema
See Clinical Presentation for more detail.
Fecal laboratory studies include the following:
Examination for ova and parasites
pH level: A pH level of 5.5 or less or the presence of reducing substances indicates carbohydrate intolerance, which is usually secondary to viral illness
Examination of exudates for presence/absence of leukocytes
Cultures: Always culture for Salmonella, Shigella, and Campylobacter spp and Y enterocolitica in the presence of clinical signs of colitis or if fecal leukocytes are present; look for Clostridium difficile in those with diarrhea characterized by colitis and/or bloody stools; assess for Escherichia coli, particularly O157:H7, with bloody diarrhea and a history of eating ground beef; screen for Vibrio and Plesiomonas spp with a history of eating raw seafood or foreign travel
Enzyme immunoassay for rotavirus or adenovirus antigens
Latex agglutination assay for rotavirus
Other laboratory studies may include the following:
Serum albumin levels: Low in protein-losing enteropathies from enteroinvasive intestinal infections (eg, Salmonella spp, enteroinvasive E coli)
Fecal alpha1-antitrypsin levels: High in enteroinvasive intestinal infections
Anion gap to determine nature of the diarrhea (ie, osmolar vs secretory)
Intestinal biopsy: May be indicated in the presence of chronic or protracted diarrhea, as well as in cases in which a search for a cause is believed to be mandatory (eg, in patients with acquired immunodeficiency syndrome [AIDS] or patients who are otherwise severely immunocompromised)
See Workup for more detail.
Acute-onset diarrhea is usually self-limited; however, an acute infection can have a protracted course. Management is generally supportive: In most cases, the best option for treatment of acute-onset diarrhea is the early use of oral rehydration therapy (ORT).
Vaccines (eg, rotavirus) can help increase resistance to infection. Antimicrobial and antiparasitic agents may be used to treat diarrhea caused by specific organisms and/or clinical circumstances. Such medications include the following:
Sulfamethoxazole and trimethoprim
See Treatment and Medication for more detail.